(麻豆淫院Org.com) -- One of the issues associated with quantum information schemes revolves around the ability to develop quantum memories that allow for the retrieval of information on demand. Overcoming this issue is especially important for the advancement of long distance telecommunications. In order to use quantum means to send information over long distance, it is necessary to implement quantum repeaters so that data is not destroyed due to the absorption loss in optical fibers.

These quantum repeaters require some sort of solid-state memory at the single photon level. And, thanks to a recent experiment at the University of Geneva in Switzerland, it鈥檚 possible that quantum information science is a little closer to application. 鈥淲e were able to show how to store and retrieve, on demand, weak light pulses at the single photon level with a wavelengths optimized for fiber transmission. This provides a direct way to interface photons used for quantum communication with a quantum memory,鈥� Bj枚rn Lauritzen tells 麻豆淫院Org.com. Lauritzen and his colleagues present their work in 麻豆淫院ical Review Letters: 鈥淭elecommunication-Wavelength Solid-State Memory at the Single Photon Level.鈥�

鈥淲e managed to reduce the noise involved with this technique as well,鈥� Lauritzen says. 鈥淲hat we have shown is a proof of principle that you can create a solid-state quantum memory for photons at telecommunication wavelengths, and this should be quite helpful in long distance quantum communications.鈥�

Lauritzen and his peers used an yttrium orthosilicate crystal doped with erbium ions to store light pulses on the single-photon level. The memory uses a photon echo technique based on controlled reversible inhomogenous broadening. 鈥淔irst, we prepared the crystal through optical pumping,鈥� Lauritzen explains. 鈥淲e prepared a narrow absorption line, which we artificially broadened using an external electrical field. When we sent in a weak pulse of light, which then was collectively absorbed by the ensemble of ions, and a de-phasing took place. We can reverse it by flipping the polarity of the electrical field.鈥�

With this method, it was possible for the Geneva team to retrieve the information it had sent in originally when it wished. 鈥淭his method is especially good for quantum repeaters, providing quantum memory at telecommunication wavelengths, making it possible to send quantum over distances not possible now.鈥�

Other applications are also possible, according to Lauritzen. 鈥淭his method could also provide a single photon source,鈥� he says. 鈥淚f you can retrieve the photon on demand, you can build up a source of photons, and command the emission of one at a time. This could be useful in a number of science experiments that require a single photon source.鈥�

The results are also interesting in terms of materials research. Exploring the properties of rare earth metals, like the erbium used to dope the crystal in the experiment, could provide some insight into new methods and techniques for future applications. 鈥淭his might stimulate some materials research, especially with erbium,鈥� Lauritzen insists.

For now, though, Lauritzen is interested in improving this technique for communication purposes. 鈥淲e鈥檙e working on memory based on atomic frequency combs, as well as testing out different conditions, such as temperature and influence of the magnetic field, to see whether we can reduce losses due to an absorbing background to increase efficiency and really make long distance quantum telecommunications 辫辞蝉蝉颈产濒别.鈥�

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